1. Field of the Invention
The present invention relates to a method for forming a hole for fitting for example, an optical fiber at a core of an optical waveguide by a laser beam.
2. Description of Related Art
Optical communication can transmit a mass of information at high speed. Therefore, it is used in various fields as basic circuits for telephone communications, LAN (local-area network) circuits, data communications between devices, or the like. An optical fiber is a medium of transmitting signals in optical communications, and the networking (branching and joining together) of light beams occurs through combining the optical fiber with an optical waveguide.
For effectively introducing a light beam into an optical fiber via an optical waveguide or for effectively introducing a light beam from an optical fiber into an optical waveguide, it is necessary that the core of the optical fiber and that of the optical waveguide be precisely matched, or accorded.
However, though the diameter of the core of the optical fiber depends on the kind thereof, it is a few or several .mu.m in the case of a single mode optical fiber of quartz, for example. Therefore, a stage device which moves with a very fine accuracy and a relative long time is necessitated for adjusting the core onto the core of an optical waveguide.
Then, in the prior art, methods for adjusting the core of an optical fiber and that of an optical waveguide by using convexo-concave insertion are already known, as disclosed for example, in Japanese Laid-open Patent Nos. Hei 5-11134 (1993) and Hei 2-33105 (1990). Further, methods for forming a hole for fitting the core of an optical fiber at a focus position are disclosed in Japanese Laid-open Patent Nos. Hei 7-244222 (1995) and Hei 7-248428 (1995).
In the disclosure of Japanese Laid-open Patent No. Hei 5-11134 (1993), a hole for fitting is formed at the core portion of an optical waveguide with a micro drill, a micro end mill and an electrodeposition sharpening stone.
In the disclosure of Japanese Laid-open Patent Nos. Hei 7-244222 (1995) and Hei 7-248428 (1995), a concavity is formed through pressing a heated conic diamond pressure member to the end surface of a lens and a convexity which is formed at the point surface of an optical fiber is fitted into the above concavity.
In the disclosure of Japanese Laid-open Patent No. Hei 2-33105 (1990), by transmitting a monitor beam incident into the core layer from one end surface of the core layer of an optical waveguide and by referencing the monitor beam emitted from the other end surface of an optical waveguide, a CO.sub.2 laser is superposed on the monitor beam so as to form a concavity for inserting an optical fiber into the core portion.
All of the methods disclosed in Japanese Laid-open Patent Nos. Hei 5-11134 (1993), Hei 7-244222 (1995) or Hei 7-248428 (1995) are not suitable for mass production since they require fine machining processes.
In the method which uses a laser beam, as disclosed in Japanese Laid-open Patent No. Hei 2-33105 (1990), it is necessary to ascertain a focus position by referencing a monitor beam and to process by finely adjusting the position of an optical waveguide on the stage device by very fine movements etc. Therefore, it takes a long period of time, resulting in a poor yield.